You can check for leaks but the only way a UPS battery would leak is if it is cracked as they are all sealed. Yes, you will not damage the computer. I had a computer plugged into a UPS with a bad battery for awhile and the beeping was driving me crazy. You would lose battery backup and voltage regulation if the UPS is with a dead battery. It depends on the model if you have AVR. You could still attach the computer to the surge protection outlet of the UPS and be covered for any surges. The UPS should have one side as battery backup and the other as surge protection only. What is the model number of the APC.
Edit: the battery is automatically charged when the UPS is plugged into an outlet. APC probably was saying the battery should be charged every 6 months if the UPS is unplugged and inactive. Hopefully your battery is okay after being charged.
Edited by JohnC_21, 18 July 2015 - 12:43 PM.